Build: Restart server on file change

[seear]

At the moment, changes to a file used on the server, including shared modules, requires the Node server to be restarted. Now that we are starting to use more shared modules, an automatic compile/restart becomes more important.

This PR changes the run target so that it:

Runs webpack --watch on server files in the background to compile on change.
Uses nodemon to restart server after compilation.

To Test
make clean
make run
Make a change to any file used on the server and check that the server restarts and picks up the change

[lamosty]

I'm just testing this and after running make clean and make run, I'm getting this error:

It's probably the "`" character it has problems with (https://github.com/Automattic/wp-calypso/blob/try/restart-server-on-change/server/bundler/index.js#L55). Interesting that it works in the master branch.

[seear]

It's probably the "`" character it has problems with

Great, thanks for spotting that, @lamosty. The nodemon command was not passing the transpiled bundle to node, hence node was tripping up on the ES6 "`" syntax.

Keep your eye open for the [Status] Needs Review labels on PRs, which are generally further along in development and need more eyes on them: https://github.com/Automattic/wp-calypso/blob/master/CONTRIBUTING.md#lifecycle-of-a-pull-request

[lamosty]

@seear Thanks. Ah, that was it.

Alright, I'll do that. Thanks for the info.

[seear]

Running webpack with & means that it won't stop with a simple ctrl+c.

[seear]

I don't believe that this is currently a desirable change. Because the client JS is built by the Node server, and there is no way to cache the compiled JS to disk, restarting the Node server means a long wait (~46 seconds on my machine) before the system is running again.

We should revisit this PR once we have a better solution for marking components as useable server-side (see #1594).